3. Chemical industry. Because of their modular design, the instruments in the TOC-L series can be equipped for any possible measurement

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1 3. Chemical industry The most commonly used compound in the chemical industry is water not only as a solvent in processing, but also as an energy carrier in the cooling or heating cycle. As vast amounts of water are needed, chemical industries are often located close to large bodies of flowing water. Water used as processing water or as cooling water is cleaned and subsequently led back to the river or stream. For environmental protection, these waters are subject to specific control and monitoring measures. As the TOC non-specifically detects all organic compounds, this parameter has also proven to be invaluable here. Large chemical industrial parks have their own wastewater treatment plants for cleaning wastewaters emanating from the various chemical plants. In order to evenly distribute the wastewater charges over the participating companies, the TOC load of the individual wastewaters is often used as a basis for calculation. Companies delivering higher TOC loads are required to pay higher charges. Incoming goods control is important in the chemical industry. Impurities present in reagents often also constitute the impurities in products. In addition to the targeted analysis of known compounds, sum parameters can help to assess the raw chemicals in terms of their impurities. The TOC plays an important role here: this parameter describes the contamination through organic compounds and specifies the total amount of organic carbon. TOC can, therefore, also be used for the assessment of inorganic chemicals. The great challenge for TOC measurements in chemical products is to develop protective mechanisms to help protect instruments and their components, as well as to prevent damage by, for instance, acid fumes or high salt loads. For this purpose, Shimadzu s TOC-L series offers several gas washers and options to ensure safe and problem-free analyses. A further challenge is to attain a stable and reproducible oxidation to ensure that no fluctuating or strongly tailing peaks are recorded. In addition, the measuring values should remain stable over a longer measuring interval. In order to cover this wide range of analytical tasks in the chemical industry, flexible systems are needed that are easily adapted to the task in question via various options, kits and modules. Shimadzu offers TOC systems that are highly suitable for such analytical problems. Because of their modular design, the instruments in the TOC-L series can be equipped for any possible measurement task. The individual application notes (for instance TOC determination in hydrochloric acid, brines or sodium hydroxide ) contain further information. In addition to applications in the chemical industry, application notes are also available on Pharmaceutical industry, Environmental analysis, TOC special applications, TOC in daily practice and TOC process analysis.

2 Sum parameter Total Organic Carbon TOC Determination in hydrochloric acid SCA Acids, in particular concentrated hydrochloric acid, represent a large group of inorganic chemicals frequently used in the chemical industry. TOC determination in concentrated hydrochloric acid poses an enormous challenge to the analyzers that are used for this purpose. In general, it is possible to greatly dilute the substance to be analyzed in order to eliminate matrix interferences. But sometimes it is necessary to achieve very low limits of detection (with reference to 37% hydrochloric acid) of 1 mg/l. TOC Measuring Method The 37% hydrochloric acid solution was manually diluted to a ratio of 1:2 with water in order to obtain an 18.5% hydrochloric acid solution. TOC-L CPH with OCT-L Acid challenge The great challenge is to develop protective mechanisms to help protect instruments and their components, as well as to prevent damage by acidic fumes. For this purpose, the TOC-L series offers several gas washers that bind and eliminate the chlorine gas formed in the flow line of the system in various ways. Another challenge is to attain a stable and reproducible oxidation process to ensure that no fluctuating or tailing peaks are being recorded. In addition, the measuring values should remain stable over a longer measuring interval. Abb.2 Mehrpunktkalibration mit Verdünnungsfunktion Calibration was carried out in the range of 0.5 to 10 ppm. The automatic dilution function of the analyzer automatically executes this calibration from a single stock solution. The injection volume was 150 µl. In case the TOC contamination of the hydrochloric acid exceeds the measuring range of the calibration, the automatic dilution function of the analyzer will readjust the hydrochloric acid solution to fit the measuring range. Verification the measuring method After calibration, the TOC content of the concentrated hydrochloric acid solution was determined.

3 SCA To investigate matrix influences, a potassium hydrogen phthalate solution was subsequently added to the 18.5% hydrochloric acid solution to increase the TOC by 5 ppm (Figure 3 and Table 1). The relative standard deviation over all measurements was 3.4%. The following graph shows the progression of the TOC values of the hydrochloric acid injections. Fig.4: Result of longterm stability Fig.3: Results of original and spiked hydrochloric solution Figure 3 and Table 1 show the results of the individual measurements of the hydrochloric acid as well as the measurements of the spiked hydrochloric acid. TOC result of 18,5% hydrochloric acid in mg/l Injection Original Spiked with 5ppm TOC 1 4,901 10,46 2 4,858 10,24 3 4,91 10,39 4 4,716 10,64 5 4,728 10,28 6 4,739 10,35 7 4,966 10,34 8 4,71 10,36 9 4,662 10, ,733 10, ,659 10, ,625 10, ,552 10,06 Mean value 4,75 10,33 SD 0,12 0,15 RSD in % 2,6 1,4 Blank values and standards (10 ppm) were alternately measured between the individual measurements. Fig. 5: Sequence of hydrochloric acid, blank (pure water) and Standards (10 mg/l) Recommended analyzer / configuration TOC-L CPH with a normal sensitive catalyst (without glass wool at the bottom of the catalyst tube) B-Type scrubber with SnCl 2 solution Copper bead scrubber with ph paper Bypassing the blank check vessel Substituting water for phosphoric acid (IC vessel) OCT-L 8-port sampler Tab. 1: Values of each injection Long-term stability To investigate the long-term stability of the method, the 37% hydrochloric acid solution was again diluted to a ratio of 1:2 with water and injected 76 times (150 µl).

4 Sum parameter Total Organic Carbon TOC Determination in nitric acid SCA Organic contaminants present in basic chemicals may constitute the impurities in products. This is why quality control of the reactants is indispensable. Calibration of the TOC-L system was carried out using the automatic dilution function in the range of 0.5 mg/l to 10 mg/l. Fig. Multi-point calibration with dilution function The determination of organic contaminations in concentrated nitric acid (69%) becomes a challenge when the required detection limit does not allow large dilution steps. An example is the TOC determination in a 69% HNO 3 solution with a detection limit of < 10 mg/l. Sample preparation For sample preparation, the 69% HNO 3 solution was diluted to a ratio of 1:10 with ultrapure water. Compound (concentration) Nitric Acid (69%) Dilution Conz. [%] 1 : 10 diluted with water (5ml / 50ml) Ca. 7% To protect the NDIR detector, the B-type scrubber was used together with the halogen scrubber. Matrix interferences In addition to CO 2, various nitrogen oxides are formed from the organic components during the combustion of nitric acid. Excessively high levels of NO 3 can lead to significant amounts of N 2 O (nitrous oxide). Nitrous oxide exhibits absorption bands in the same IR detection range as CO 2 and can, therefore, be misinterpreted for CO 2. In addition, nitrous oxide can cause tailing and can affect the peak symmetry. Due to the high solubility of N 2 O in water, the gas is dissolved in the B-type scrubber and will not reach the detector.

5 SCA Result The duplicate NPOC determination of a nitric acid produced the following results: Sample Nitric Acid (69%) Nitric Acid (69%) NPOC [mg/l] RSD [%] 36,9 1,4 33,4 3,0 To investigate this matrix influence, an additional dilution (1:10) of a 69% nitric acid solution was carried out and a potassium hydrogen phthalate stock solution was subsequently added to increase the NPOC content by 5 ppm. (Note: This corresponds to an increase to 50 ppm for the 1:10 dilution). Recommended Analyzer / Configuration TOC-L CPH with normal sensitive Catalyst B-Type-Scrubber OCT-L (8-port Sampler) Sample NPOC RSD [mg/l] [%] Nitric Acid (69%) 25,1 1,3 Nitric Acid (69%) Spiked with 50 ppm KHP 76,2 1,8 The use of suitable gas washers (scrubbers) enables reproducible TOC measurements in concentrated nitric acid.

6 Sum parameter Total Organic Carbon TOC Determination in sulfuric acid SCA Acids are a group of frequently used inorganic chemicals used in the chemical industry. In particular, sulfuric acid is used in a wide range of applications. The following SO 2 scrubbers are available: Sulfix (WAKO Chemicals, Fuggerstr. 12, Neuss, Germany). The Sulfix scrubber is installed underneath the normal sensitive catalyst and enables selective filtration of the formed SO 2. Mist scrubber (cartridge) Just like the halogen scrubber, the Mist scrubber is used in the flow line for SO 2 absorption. In the experiment described below, the NPOC content of a 98% sulfuric acid solution is determined. Sulfuric acid in a concentration range to 1%.can be directly measured using a TOC-L analyzer Higher sulfuric acid concentrations can lead to tailing and, consequently to increased measurement values because high sulfate concentrations (> 5000 mg/l) can lead to the formation of large amounts of SO 2 vapors. SO 2 exhibits absorption bands in the same IR detection range as CO 2 and can, therefore, be misinterpreted for CO 2. To determine organic contaminations in highly concentrated sulfuric acid, additional SO 2 scrubbers are used. The required purity criterion and the required limit of detection was < 10 mg/l. Sample preparation The concentrated sulfuric acid was diluted with ultrapure water to a ratio of 1:10 to decrease the concentration as well as the viscosity of the sulfuric acid. Compound (Concentration) Dilution Conc. Sulfuric acid (98%) 1 : 10 diluted with water (5m/50ml) Ca. 10% The dilution has to be carried out with the utmost care and caution, as the sulfuric acid reacts violently upon the addition of water (heat generation).

7 SCA The system is calibrated using the automatic dilution function in the range of 0.5 mg/l to 10 mg/l. Result The duplicate determination of sulfuric acid yielded the following results: Sample Sulfuric acid (98%) Sulfuric acid (98%) NPOC [mg/l] RSD [%] <10 (4,6) - <10 (5,4) - Fig. Multi-point calibration with dilution function Kit for high-salt samples For the determination, a TOC-L CPH equipped with a kit for high salt loads was used. The kit consists of a special catalyst tube, a special mixture of various catalyst beads and a ceramics grid, which replaces the platinum net. The sulfuric acid fulfilled the required purity criteria of TOC < 10 mg/l. The use of suitable gas washers (scrubbers) enables reproducible TOC measurements in concentrated sulfuric acid. Sample acidification when using the high-salt kit, is carried out with sulfuric acid. Sulfuric acid is used to modify the sample matrix. While NaCl has a melting point of 801 C, the melting point of NaSO 4 is higher (881 C). This has a positive effect on the lifetime of the combustion tube. For this reason, sulfuric acid is measured directly using the high-salt kit. Recommended analyzer / Configuration TOC-L CPH OCT-L High-Salt-Kit B-Type-Scrubber with diluted hydrochloric acid with wire net. Mist-Scrubber

8 Sum parameter Total Organic Carbon TOC Determination in brines SCA The determination in difficult matrices, such as brines or heavily contaminated wastewaters, presents a special challenge for TOC analyzers. In the chemical industry, brines with a salt load (NaCl) of up to 28% are used for chlor-alkali electrolysis. For this process it is important to know the TOC content. The unique feature of this application does not inherently lie in the conversion of the carbon components to carbon dioxide, but in the salt load associated with the matrix. This leads to higher maintenance needs, as the salt can crystallize in the combustion system. Kit or high-salt samples The TOC-L series features a kit for high-salt samples, which significantly increases the instrument s availability. The kit consists of a combustion tube of a special geometry and a unique catalyst mixture. In this application, sample acidification is carried out with sulfuric acid. Sulfuric acid modifies the sample matrix. Whereas the melting point of NaCl ia 801 C, NaSO 4 has a higher melting point is (888 C). The potassium salts of sulfuric acid also have a significantly higher melting point than those of hydrochloric acid. This extends the lifetime of the combustion tube. Compound Melting point NaCl 801 C KCl 773 C Na 2 SO C MgCl C CaCl C K 2 SO C Tab. Melting point of different salts Sample preparation The determination of organic contaminations in a pure brine (30% sodium chloride solution) is described below. For such highly concentrated salt solutions, the principle of diluting the sample as much as possible applies. As the required detection limit was at < 1 mg/l, the samples were diluted with ultrapure water to a ratio of 1:1. Dilution was carried out manually in a 50 ml volumetric flask under the addition of several drops of concentrated sulfuric acid (25%).

9 SCA Compound (Concentration) Brine solution (30%) Dilution 1 : 2 diluted with water (25ml/50ml) add. 1-2 drops Sulfuric acid until ph<7 Conc. ca. 15%ig Initially, a blank value and a control standard (10 mg/l) were measured, and the NaCl solution was subsequently injected. The control standards were tested after 110 and 220 injections of the brine solution, respectively. For the analysis a TOC-L CPH equipped with a kit for high salt loads was used. The system is calibrated using the automated dilution function in the range of 0.5 mg/l to 10 mg/l. Maintenance of the combustion tube and the catalyst was not necessary after the measurements were completed. Only the TCslider needed to be cleaned. The figure above shows the excellent reproducibility s and the stability of the measurement. Fig. Multi-point calibration with dilution function Result The duplicate determination of the TOC analysis yielded the following results: Sample NPOC RSD [mg/l] [%] Brine solution (30%) 3,6 1,8 Brine solution (30%) 3,6 1,8 Stability test In this test, the long-term stability of the combustion system was tested. The system was calibrated to 10 mg/l with an injection volume of 50 µl. A 28% NaCl solution was prepared and spiked with a KHP solution to obtain a 5 mg/l TOC solution and a 15% sulfuric acid solution was added. Recommended Analyzer / Configuration TOC-L CPH High-Salt-Kit B-Type-Scrubber

10 Sum parameter Total Organic Carbon SCA TOC Determination in sodium hydroxide solution Organic contaminants in basic chemicals may lead to impurities in the products. Therefore, quality control of the reactants is necessary. The TOC determination in sodium hydroxide can lead to various problems. The catalyst and the combustion tube wear out very rapidly. This, in turn, will lower the sensitivity at an equally fast rate and leads to very poor reproducibilities. NaOH can also absorb CO 2 from the environment. As air contains approximately 400 ppm CO 2, direct TC determination in sodium hydroxide can lead to much higher values. The NPOC method is, therefore, recommended for the determination of organic contaminations in sodium hydroxide. The sample should also be diluted as much as possible. Several ml of ultrapure water were placed in a 50 ml volumetric flask. Subsequently, 5 ml of the concentrated sodium hydroxide was pipetted into the flask. Finally, concentrated sulfuric acid was added until the solution has reached a ph < 2. The flask was then filled with ultrapure water up to the mark. The addition of sodium hydroxide, as well as the addition of sulfuric acid to the water must be done with the utmost care and caution, as a violent chemical reaction occurs. Compound (Concentration) Sodium hydroxide solution (50%) Dilution 1 : 10 diluted (5 ml / 50 ml) add. 1-2 drops Sulfuric acid until ph<7 (Note: generation of heat) Conz. [%] approx. 5% + Sulfuric acid Calibration of the TOC-L system was carried out using the automatic dilution function within the range of 0.5 mg/l to 10 mg/l. In the present case, a 50% sodium hydroxide solution was analyzed. The purity criterion and the required limit of detection was < 10 mg/l. Sample Preparation The sample was first manually diluted to a ratio of 1:10 with ultrapure water and a suitable amount of acid. Fig. Multi-point calibration with dilution function

11 SCA Kit for high salt samples For the determination, a TOC-L CPH was equipped with a kit for high salt loads. The kit consists of a special catalyst tube, a special mixture of various catalyst beads and a ceramics grid, which replaces the platinum net. Signal[mV] Zeit[min] Fig. Example peaks of 50% sodium hydroxide solution Recommended Analyzer / Configuration When using the high-salt kit, sample acidification is carried out with sulfuric acid, which is used here to modify the sample matrix. Compared to NaCl with a melting point of 801 C, the melting point of NaSO 4 is higher (881 C) which extends the lifetime of the combustion tube. TOC-L CPH OCT-L (8-port samples) High-Salt-Kit B-Type-Scrubber Results The 5% sodium hydroxide can now be measured using the NPOC method. The duplicate determination of the sodium hydroxide yielded the following results. Sample Sodium hydroxide (50%) Sodium hydroxide (50%) NPOC [mg/l] RSD [%] <10 (8,2) - <10 (8,3) - The sodium hydroxide met the required purity criteria of < 10 mg/l TOC.

12 Sum parameter Total Organic Carbon TOC Determination in soda solution SCA Impurities in products can be caused by organic contaminants present in basic chemicals to. That is a reason why quality control of the reactants is indispensable. In the case described here, a 50% soda solution was investigated. The required detection limit was 10 mg/l. Sample preparation The sample was first manually diluted to a ratio of 1:10 with ultrapure water and a corresponding amount of acid. Several ml of ultrapure water were placed in a 50 ml volumetric flask. Subsequently, 5 ml of the concentrated soda solution was pipetted into the flask. Finally, concentrated sulfuric acid was added until the solution has reached a ph < 2. The flask was then filled with ultrapure water up to the mark. Compound Dilution Conc. (Concentration) Soda hydroxide solution (50%) 1 : 10 diluted with water (5ml/50ml) add. 1-2 drops Sulfuric acid until ph<7 Approx. 5% In the determination of organic contaminations in concentrated soda solutions, various issues must be considered. In comparison to organic carbon, the soda solution to be investigated has a very high inorganic carbon content in the form of carbonates. In addition, the solution has a high ph value and tends to absorb carbon dioxide from the air. Caution: During the addition of the sulfuric acid, the carbonates decompose under a violent reaction (heat dissipation / gas formation). A soda solution must, therefore, be analyzed using the NPOC method.

13 SCA Calibration of the TOC-L system was carried out using the automatic dilution function in the range of 0.5 mg/l to 10 mg/l. The higher melting point point of NaSO 4 (881 C) compared to NaCl (801 C) has a positive influence on the lifetime of the combustion tube. Results The duplicate determination of the soda solution yielded the following results: Fig. Multi-point calibration with dilution function Sample Soda solution (50%) Soda solution (50%) NPOC [mg/l] RSD [%] 56,4 7,1 54,8 4,9 For the determination, a TOC-L CPH was equipped with a kit for high salt loads. A special catalyst tube, a special mixture of various catalyst beads and a ceramics grid, which replaces the platinum net are part of the kit. Signal[mV] Zeit[min] Fig. Peak graphs of a diluted soda solution (ca.5%) Sample acidification when using the high-salt kit, is carried out with sulfuric acid in order to modify the sample matrix. Recommended Analyzer / Configuration TOC-L CPH ASI-L High-Salt-Kit B-Type- Scrubber

14 Sum parameter Total Organic Carbon SCA TOC Determination in ammonia or ammonium salt solutions Basic chemicals may contain organic contaminants polluting end products. This is why quality control of the reactants is a must. In the TOC determination of ammonia water or concentrated ammonium salt solutions, various issues must be considered. Ammonia and some ammonium salts are alkaline. The catalyst and combustion tube are sensitive to alkaline media and are subjected to increased wear. Sample preparation The ammonium nitrate solution was diluted with ultrapure water to a ratio of 1:10. Dilution was carried out manually in a 50 ml volumetric flask under addition of several drops of concentrated sulfuric acid (25%). Compound (Concentration) Ammonium nitrate solution (40%) Dilution 1 : 10 diluted (5 ml / 50 ml) add. 1-2 drops Sulfuric acid until ph<7 (Note: generation of heat) Conc. Approx. 4% Calibration of the TOC-L system was executed using the automatic dilution function in the range of 0.5 mg/l to 10 mg/l. The solutions should, therefore, be acidified and possibly be diluted. The decomposition during oxidation of the ammonium or ammonia proceeds to completion without the formation of residues on the catalyst. Therefore, it is not necessary to use a high-salt kit. In the case described below, the NPOC content of a 40% ammonium nitrate solution was determined. The required detection limit was < 10 mg/l. Fig. Multi-point calibration with dilution function

15 SCA Interferences In addition to CO 2 formed from the organic components, various nitrogen oxides are formed during the combustion of ammonium salts or ammonia water. Excessively high nitrogen levels can lead to the formation of significant amounts of N 2 O (nitrous oxide). Nitrous oxide exhibits absorption bands in the same IR detection range as CO 2 and can, therefore, be misinterpreted for CO 2. In addition, nitrous oxide can cause tailing and can affect the peak symmetry. A B-type scrubber is used to eliminate possible interference by nitrous oxide. Due to the high solubility of N 2 O in water, the gas is dissolved in the B-type scrubber and will not reach the detector. Signal[mV] Zeit[min] Fig. Example peaks of 40% ammonium nitrate solution Results The duplicate determination of the ammonium nitrate solution yielded the following results: Recommended analyzer / Configuration Probe Ammonium nitrate solution (40%) Ammonium nitrate solution (40%) NPOC [mg/l] RSD [%] 56,5 0,8 56,7 1,2 TOC-L CPH OCT-L (8-port sampler) B-Type- Scrubber

16 Sum parameter Total Organic Carbon SCA TOC Determination in sodium nitrate and sodium nitrite Basic chemicals may contain organic contaminants influencing the quality of products. Quality control procedures of the reactants are, therefore, necessary in order to detect impurities. For the determination of organic contaminations in salts, solutions of these salts can be prepared and subsequently measured using a TOC-L analyzer. Compound (Concentration) Sodium nitrate (>99,9%) Sodium nitrite (>99,9%) Dilution Weighted Sample 5 g / 50 ml add. 1-2 drops Sulfuric acid until ph<7 Weighted Sample 5 g / 50 ml add. 1-2 drops Sulfuric acid until ph<7 Caution: Nitrogen oxide gas is released Conz. approx. 10% approx. 10% Caution: Nitrite salts react to form of toxic nitrous gases. Sample preparation should, therefore, always be carried out under a hood. The samples should only be removed from the hood, when no more nitrous gases escape. High salt concentrations generally present a problem for TOC analysis. These salts can crystallize in the combustion system and lead to higher maintenance needs. Calibration of the TOC-L system was done applying the automatic dilution function in the range of 0.5 mg/l to 10 mg/l. In the case described below, the NPOC content of two salts was determined. The difficulty was the required detection limit of 10 mg/kg. Sample preparation For sample preparation, 5 g of both salts (sodium nitrite and sodium nitrate) were weighed into a 50 ml volumetric flask and diluted with ultrapure water. During dilution, the solutions were acidified with concentrated sulfuric acid (25%). Fig. Multi-point calibration with dilution function

17 SCA Kit for high-salt samples The TOC-L series features a kit for high-salt samples, which significantly increases the instrument s availability. The kit consists of a combustion tube of a special geometry and a unique catalyst mixture. Results The duplicate determination of the salt solutions yielded the following results: Sample NPOC [mg/kg] RSD [%] Sodium nitrate (>99,9%) 22,8 4,7 Sodium nitrate (>99,9%) 24,0 6,8 Sodium nitrate (>99,9%) <10 (9,0) Sodium nitrate (>99,9%) 10,2 5, Signal[mV] Zeit[min] Fig. Example peaks: Sodium nitrate In this application, sample acidification is carried out with sulfuric acid which is used to modify the sample matrix. Due to the higher melting point of NaSO 4 (888 C) compared to 801 C of NaCl the lifetime of the combustion tube is longer. Interferences The combustion of nitrogen compounds can lead to the formation of nitrous oxide gas. Nitrous oxide exhibits absorption bands in the same IR detection range as CO 2 and can, therefore, be misinterpreted for CO 2. In addition, nitrous oxide can cause tailing and can affect the peak symmetry. Recommended Analyzer / Configuration TOC-L CPH ASI-L High-Salt-Kit B-Type-Scrubber A B-type scrubber is used to eliminate possible interference by nitrous oxide. Due to the high solubility of N 2 O in water, the gas is dissolved in the B-type scrubber and will not reach the detector.

18 Sum parameter Total Organic Carbon TOC determination in phosphoric acid No. SCA Phosphoric acid is one of the most frequently used inorganic acids in industrial applications. It is applied as starting material for the manufacture of phosphate-containing fertilizers as well as for the production of water-softening agents such as detergent additives. Phosphoric acid is also used in the food industry as acidification agent and preservative in beverages or as antioxidant in meats and meat products. because the phosphoric acid damages the combustion tube and the catalyst. Due to this, the wet chemical TOC method is used to measure TOC in phosphoric acid. Wet-chemical UV oxidation at 80 C The determination of the TOC content in phosphoric acid is carried out via wetchemical UV oxidation using Shimadzu s TOC-V WP. Particularly for these types of applications, it is important to apply acids that are pure and free from foreign substances. Manufacturers and processors of phosphoric acids are increasingly using the TOC (Total Organic Carbon) sum parameter for quality control. This parameter is a measure of the contamination of phosphoric acids by organic components. The TOC method by using the catalytic combustion is not suitable for the determination of phosphoric acid, Its core technology is the powerful oxidation applying a combination of sodium persulfate and UV oxidation at 80 C. This ensures that all dissolved carbon compounds are converted to CO 2. In the presence of persulfate ions and UV illumination, OH-radicals are formed which have a strong oxidative effect and convert organic compounds to carbon dioxide. A carrier gas transports the carbon dioxide formed to the NDIR detector where they are detected.

19 SCA Automated reagent preparation eliminates any contamination of the reagent solutions and minimizes the blank value of the instrument. TOC determination Due to lower TOC concentration, the instrument is calibrated in a range of 0,1 1 mg/l. The autosampler OCT-1 has a big advantage for the measurement of aggressive matrices, because its parts are done of Teflon. Method of phosphoric acid measurement The concentrated phosphoric acid (85%) is diluted by 1:5. TOC determination in phosphoric acid was carried out using the NPOC (Non-Purgeable Organic Carbon) method. Prior to TOC determination, neutral or alkaline samples are acidified in order to decompose all inorganic carbonates and bicarbonates. This step could be omitted for phosphoric acid. Figure: Calibration of NPOC between 0,1 1 mg/l. Concentration of the phosphoric acid does not play a significant role in the determination; it is only necessary to ensure that the acid is not too viscous. The 85% phosphoric acid solution was therefore diluted 1:5 with water. The resulting 17% acid solution was transferred into the instrument using an OCT- 1 autosampler. Acidification: 0% Sparge-time: 2 minutes Injection volume: 3000µl Results Abb.: Peak graph of diluted phosphoric acid(17%) The 17% phosphoric acid solution measured in this way resulted in a TOC concentration of 0.61 mg/l. The relative standard deviation over three injections was 1.8%. Recommended Analyser / Configuration - TOC-V WP/WS - OCT-1

20 Sum parameter Total Organic Carbon SCA TOC Determination in diluted hydrofluoric acid Hydrofluoric acid is the only acid that attacks glass (glass etching). Because of this chemical property, it plays a distinct role in several industrial processes, for instance in the manufacturing of solar cells and wafers as well as in microchip production. Hydrofluoric acid is the most widely used etching agent in the semiconductor industry. TOC determination In the following measurement, a 4% hydrofluoric acid was manually diluted to 1:10 with water and measured using the TOC- L CPH. Given the acidity of the hydrofluoric acid, the IC content can be neglected. With regard to the dilution, the solution was slightly acidified and sparged for 3 minutes. The NPOC was subsequently determined by means of combustion oxidation. An aliquot of the sample is injected onto a hot (680 C) platinum catalyst. The organic substances are converted to CO 2 and detected via an NDIR detector. When carrying out etching processes, it is important to ensure that the etching agent used will etch the respective layers and not leave any contaminants. Calibration Due to mostly working in a small measuring range, calibration was carried out in a range of 0.25 mg/l 5.0 mg/l. For dilutions, the automatic dilution function of the TOC-L system was applied. The injection volume was 150 µl respectively. This raises questions on the impurities of etching agents, where both the purity of the starting acid and that of the etching solutions after the etching process are of interest. To determine the degree of contamination, the TOC parameter is particularly suitable, as it is a sum parameter that detects all organic carbon compounds. Fläche 69, Kal. Kurve ,5 Konz[mg/L] Figure: Calibration curve, TC 5 mg/l.

21 SCA Measurement example A total of 3 different hydrofluoric acids (0,4%) were measured: - Hydrofluoric acid prior to etching (HF1) - Hydrofluoric acid after etching (a seemingly clean wafer (HF2)) - Hydrofluoric acid after etching (a seemingly dirty wafer (HF3)) NPOC method Acidification: 1.5% Purging time: 3 minutes Injection volume: 150 µl Number of injections: 3 Protection and safety For such measurements, comprehensive protective measures for dealing with hydrofluoric acid must be urgently observed. This also includes wearing protective clothing, gloves and safety goggles. Signal[mV] Zeit[ After measurement, the instrument must be rinsed several times with water. In addition, 20 injections with ultrapure water must be carried out. Nevertheless the lifetime of syringe, combustion tube and catalyst will be shortening, due to HF solution. Figure: Peaks of the diluted HF solution. The measurements were already stable after two or three injections. It is advantageous to carry out several HF injections prior to the actual sample measurement. Recommended instrument/ equipment TOC-L CPH / CPN OCT-L Results Sample NPOC [mg/l] RSD [%] HF HF HF